Apparatus for determining ballistic factors



April 2, 1946. H. c. FORD APPARATUS FOR DETERMINING BALLISTIC FACTORS Filed July 271 1928 INVENTOR (H CF07"? 9-if TTORNEYS %%\.J V15 m mm &% mmwm Mm IN an g m -Mm Nu E 7 SQ m NM v w 7 s w m w 2 A m k if 4 e 9 3 m u n N i Patented Apr. 2, 1946 APPARATUS FOR DETER i FACTORS Hannibal C. Ford, Jamaica, N. Y assignor to Ford Instrument Company, Inc., Long Island City, N. Y., a corporation of New York Application July 21, 1928, Serial No. 294,497

12 Claims.

This invention relates to an apparatus for determining the values of ballistic factors involved in the firing of ordnance.

More specifically the invention provides an apparatus using the method of determining the value of a-ballistic factor afiecting the trajectory of'a projectile fired in accordance with a point of aim which consists in calculating the firing data for the point of aim and an estimated value of the ballistic factor, firing a projectile in accordance with the firing data, observing the diflerence between the point of impact of the projectile and the point of aim and determining the actual value of the ballistic factor by altering it until the calculated firing data is altered by the amount of the observed difference.

One form of apparatus which may be employed consists of an instrument for computing the corrections due to ballistic factors, such as the initial velocity of a projectile and the effect of wind upon a projectile and which includes mechanism whereby the values of the ballistic factors set up in the instrument may be corrected as a result of observations of the errors in the firing the factors as originally set up in the instrument.

The particularnature of the invention as well as other objects and advantages thereof will appearmore clearly from a description of a preferred embodiment as shown in the accompanying drawing in which:

Fig. 1 is a diagrammatic view of the instrument, and

Fig. 2 is a ballistic diagram used in connection with the explanation of the operation of the instrument.

Referring to Fig. 1, I represents a shaft provided with a crank 2 by which the range of the point of aim of the guns with which the instrument is to be used may be set into the instrument, the value of the range being shown by a dial 3 reading against an index i and carried on a shaft 5 connected througn'bevel gears t to the shaft I.

The shaft i is also connected by two pairs of bevel gears i with two screws 8 of varying pitch passing through the ends of a range bar 9 extending between the screws and provided with pins 9' extending into their threads; The bar 9 carries a slidable carriage H) from the front side of which a pin il projects through a slot in an arm I 2 which at its upper end is slidably mounted on a pin l3 projecting from a fixed frame member H. The lower end of the arm I: is pivoted to a horizontal rack l5 meshing with a pinion It on one end of a shaft H. the other end of which carries an initial velocity dial l8 readable against an index I9. The shaft ll also carries a gear meshing with a pinion 2| on the shaft of a motor 22, the circuits and function of which will hereinafter be described. The gear 20 also meshes with a pinion 23 on a longitudinally movable shaft N provided with a crank 25 at its outer end. The inner end of the shaft is rotatably mounted in the free end of a switch spring 26 provided with a contact element 21 and mounted within a block of insulation 28. A

go initialvelocity slide 32 the horizontal arm of which is provided with a rack meshing with a pinion 33 attached to one side 34' of a difierential 36, the remaining elements of which will be hereinafter described.

The shaft i is also provided with two pairs of bevel gears 35 for driving screws 36 of varying pitch which pass through the ends of a range bar 31 having pins 31' extending into the threads of the screws. The bar carries a slidable carriage 38 having a, rearwardly projecting pin 39 which passes through a slot in an arm 40 which is slidably mounted at its upper end upon a pin 4H projecting from a fixed frame 42. The lower "end of the arm is .pivotally connected to a horizontal rack 43 which meshes with a pinion 44 on one end of a shaft t5 which carries on its other end a dial t6 readable against an index 41 for showing the wind component along the line of sight to a target. The shaft also carries a gear 48 meshing with a pinion 49 on the shaft of a motor 50, the circuits and function of which will be hereinafter described.

The gear 48 also meshes with a pinion 5| on a longitudinally movable shaft 52 provided at its outer end with a crank 53. The other end of the shaft is rotatably connected to a switch spring 54 provided with a contact element 55 and mounted in a block of insulation. A second switch spring 55 carries a coacting contact element 51 and is also mounted in the block.

The carriage 38 is provided with a pin 58 extending forwardly and in alignment with the pin 39 through the slotted vertical arm of a rectangular wind component slide 59, the horizontal arm of which is provided with a rack engaging a pinion 60 attached to the second side 34" of the differential 34. The center- 34" of the differential is attached to a shaft 6i connected by bevel gears 62 to a shaft 63 which carries a gear 60 meshing with a gear 65 attached to one side 66' of a difierential 66. The other side 66" of the difierential carries a gear 61 meshing with a pinion 60 on the end of a shaft 60 which is connected through bevel gears 10, shaft II, bevel gears 12, shaft 13 and bevel gears 14 to the side 15' of a differential 15, the center 15" of which is attached to the right hand end of shaft I.

The second side of this differential is connected by bevel gears 16 to a shaft 11 carrying a dial 10 readable against an index 10 to show the firing range, that is, the range corrected for initial velocity and wind component as will hereinafter be explained in detail. The shaft 13- also 1 drives through bevel gears 00 and shaft BI, a dial 02 readable against an index 03 to show the value of the corrections applied to the range to give the firing range shown by the dial 10.

The shaft 69 also carries a gear 04 meshing with a gear 05 on .the shaft of a motor 06 the circuits of which will be hereinafter described. Adapted to coact with gear 84 under certain conditions is a pinion 81 on a shaft 88 provided with a crank 80. The other end of this shaft is rotatably mounted in a switch spring 00 provided with contact elements 9| and 92 and mounted in a block of insulation 03. The contact element 3! coacts with a similar element 90 at the end of a switch spring 95 mounted in the block 93. The contact element 02 coacts with a similar element 06 at the end of a switchspring '91 also mounted inthe block. 03.

The center 60" of the differential 66 is attached to a shaft 08 which carries on its other end a cam 99 formed with two dwells of unequal normal relation of the parts being such that the roller engages an intermediate point of one of the sloping portions of the cam so that when to switch spring 26. The coacting switch spring 29 is connected by conductor II5 to a contact element with which the blade II6 of a doublethrow switch is adapted to coact, this blade being connected by conductor II1 to switch spring 96. The armature of motor 60 is connected by conductor M8 to the switch spring 64 and the coacting switch spring 66 is connected by conductor II9 to the other contact element for the switch blade H6. 1

In the initial operation of the apparatus the parts may be regarded as occupying the positions illustrated. The range of the target as determined by a suitable instrument is applied by rotatingthe handle 2 and shaft I until the proper value is indicated by the dial 3. The movement of the shaft I produces a displacement of the range bar 0 through bevel gears 1 and screws 8 and of the range bar 31 through bevel gears the cam turns in one direction the roller is moved inwardly against the dwell of lesser radius by the tension of the spring, while if the cam turns in the opposite direction the roller is moved outwardly against the tension of the spring, into engagement with the dwell of greater radius. The upper portion of the lever is insulated from the lower portion and is formed at its outer end as a contact I00 lying between a pair of contacts I00 and I00.

The electrical elements of the apparatus are energized as will hereinafter be described from supply mains I05 and W6 through the following circuit connections. A conductor I01 is connected between the main I05 and the upper por- 35 and screws 36. It is intended that the parts shall be so arranged that for normal initial velocity of the projectile the arm I2 will occupy a vertical position and the same is true of the arm 40 for zero value of the wind component along the line of sight.

If the initial velocity differs from its normal value the crank 25 will be manipulated to turn the shaft 24 and through pinion 23 and gear 20 drive the shaft I1 until the desired value as shown by the dial i8 is set up. Through pinion I6 there will be a corresponding movement of rack I5 and arm I2 to displace through the pin II the carriage I0 on the range bar 0. The pin 3| will thus be displaced in accordance with the.

amount by which the difference in initial velocity affects the range. The screws 8 are of variable pitch to take care of the variable function of initial velocity with respect to range. The resulting displacement or the pin 3! will move the slide 32 and the side 34' of the differential 36 through pinion 33. In other words, this side of the differential will be displaced in accordance with the initial velocity correction for the given range of the target.

In a similar manner the correction required for the estimated wind component along the line of sight is introduced by manipulation of the crank 53 to turn the shaft 52 and through pinion 5i and gear 48 rotate the shaft t6 until the required value hasbeen set up as shown by the dial 56. Through pinion 44; the rack 43 and arm 00 will be correspondingly displaced to alter through the pin 39 the position of the carriage 38 on the range bar 31. The screws 36' are of variable pitch to take care .of the variable function of the wind component with respect to range. The pin 58 is thus displaced in accordance with the estimated effect of the wind component on the range of tion of the arm I00. The main I06 is connected of reversely wound field windings connected to' conductors H0 and III. These conductors are connected respectively to contacts I04 and I04 and also to conductors H2 and H3, respectively,

connected to the oppositely wound field windings of the motors 22 and 50 which willbe understood to be of the same type as motor 86.. The armature of motor 22 1s connected by conductor H4 the target. The slide 50 is thus correspondingly displaced as is also the side 30" of difierential 34 by pinion 60.

The center 34" of the differential is thus displaced in accordance with the combined initial velocity and wind corrections for the range of the target. Through shaft 6|, bevel gears 62, shaft 63 and gears 64 and 65 the side 66' of differential 66 is correspondingly displaced. Regarding for the time being the side 66" as fixed the center 66" will be turned and through the shaft 08 turn the cam 99 in one direction or' the other to shift the contact I00 into engagement with contact I04 or contact I04 according to ,whether the lower end of the lever I00 moves inwardly or outwardly from its normal position with respect to the cam.

A circuit will thus be established from the main I05 through conductor I01, lever I00, contact I00, one or the other of the contacts I04 or I04 and conductors I I0 or II I, the corresponding field winding of the motor 00, the conductor I09,

switch spring 01, contact elements 96 and 92,-

switch spring 00 and conductor I00 to the other main I06. The energization of the motor will through gears 85 and 04, shaft 09, pinion 68 and ear 6? drive the side 65" of the differential 66. Regarding the other side 66' as fixed the center 66" will be turned in the opposite direction to which it had been previously turned to break the circuit of the motor 86 by restoring the lever I 00 to its normal position with its roller I 02 engaging the sloping portion of the cam 99. The elements thus described, constitutea follow-up system by which the shaft 09 is driven in accordance with the movement imparted to shaft 63, but with increased power furnished by the motor 06.

The movement of shaft 60 is transmitted through bevel gears 10, shaft H and bevel gears I2 to the shaft 13. Through bevel gears 00 and shaft M, the dial 02 is turned to show the correction applied to the range to give the firing range. At the same time the side 75' of the differential 75 is driven from the shaft 13 through bevel gears l4 and since the center 15" of this differential is driven by the shaft i the second side 75" will be turned in accordance with the algebraic sum of range and the corrections therefor, so that through bevel gears It and shaft 17, the dial 18 will be turned to show the value of the firing range for the estimated corrections for initial velocity and wind component along the line of sight. g

The gun will then be fired in accordance with the indicated range and its projectile will have a trajectory represented by the broken line A of Fig. 2 with a point of impact B, it being understood that the term "point of impact as used herein includes the point of burst of time fuse projectiles, such as are used against air craft. If the initial velocity and wind component corrections have been correctly evaluated one of these quantities being known and the other being estimated, the point of impact will be at the required point of aim, but in practice there will usually be errors in the estimates of either or both of these quantities so that the actual trajectory A diflers from the desired trajectory C with a difference between the point of impact B and the desired point of aim D. As stated above, this difference may be due to an error in the estimated initial velocity of Y the gun or to an error in the estimated wind component along the line of sight or to a combination of errors in both quantities. Since the actual value of the initial velocity can usually be accurately estimated and an error in the estimated wind component is more probable the manner in which corrections are applied to the apparatus will be described in connection with the wind component elements, it being understood that a similar operation may be performed in connection with the initial velocity elements and also in connection with both of I Ordinarily, this is obtainable from standard range data which give the initial velocity for guns and modified, if necessary, forknown gun erosion, for example.

To put the apparatus in condition to be cor- I rected the crank 53 and shaft 52 are moved fortime contact elements 9| and 04 are brought into engagement to connect the conductors I 00 and I I1 through the switch springs 00 and 05.

The crank 89 is then manipulated in accordance with the estimated corrections required to compensate for the error in the trajectory of the pro- Jectiles due to the error in the initial estimate of the wind component along the line of sight. The rotation imparted to the shaft 88 will be transmitted through pinion 01 and gear to shaft 69 and from the latter through bevel gears I0, shaft II, bevel gears I2, shaft I3, bevel gears I30 and shaft BI to the dial 82 to show when the estimated correction has been properly set up in the instrument. At the same time the shaft 69 will through pinion 00 and gear 61 turn the side 66" of differential 60. Regarding its other side 66' as fixed the center will be turned to displace the cam 09 through shaft 08 in one direction or the other to establish a circuit from the mainIOE through conductor I01, lever I00, contact I00, one or the other of the contacts IM or I00, one or the other of the conductors H0 or III, the corresponding field winding of the motor 50, conductor II 8, switch spring 54, contact elements 55 and 51, switch spring 56, conductor I I9, switch blade H6, conductor III, switch spring 95. contact elements 90 and BI, switch spring 90 and conductor I 00 to the other main I00.

The energization of motor 50 causes through pinion 49, gear 08, shaft 85 and pinion M a correctional movement of the wind component rack t3. There will, therefore, be a corresponding displacement of the pin 58 and slide 59 which will be imparted to the side 34" of differential 34 through pinion 60. Regarding the other side 35' -now fixed the center 86" will be turned in a direction to restore the cam 99 and lever I00 to their normal relation with the roller I02 upon one of the sloping portions of the cam thereby breaking the circuit of motor 50.

The correctional displacement of the shaft 73 produced by manipulation of the crank 89 will also be transmitted through bevel gears 14 to the side I5 of the differential I5 and regarding its center 15" as fixed the second side 15" will be turned to produce a corresponding correctional displacement of the firing range dial 18.

As a, result of the correctional operations described above the wind component slide59 will be displaced in accordance with the required correctlon so that when the parts are restored to the condition shown inFig. 1 this wind correction will be automatically and continuo sly applied to the range to indicate the correct firing range for changing values of range set up by operation of crank 2.

In practice the instrument will be so manipulated as to bring the point of impact .6 to the point of aim D by a series of correcting operationsas described above. When such a condition exists the indications of the dial 46 will show the actual wind component along the line of sight, this value being subject to corrections from time to time due to changes in wind.

As stated above when the actual value of the tween the estimated and actual initial velocities may be applied as described above in connection with wind, with the difference that the switch blade H6 is shifted to itsright hand position and the crank 25 is moved forwardly to disengage the pinion 23 from gear 20 and partially establish the circuit of motor 22 through conductor Ill, switch spring 26, contact elements 21 and 30, switch spring 29 and conductor M5 to the switch blade i It from which the circuit continues to the main Hi6 over the elements previously described. The motor 22 is then controlled by the actuation of the cam 99 from differential 66 to produce a, correctional displacement of the initial velocity slide 32 to maintain the parts of the instrument in corrected condition when restored to their normal condition. As in the case of the wind component, the correct value of the initial velocity will be indicated by dial it after the correcting operations have been performed.

While the apparatus has been shown in connection with a wind component along the line of sight it will be understood that a similar apparatus may be used for determining the corrections due to a wind component perpendicular to the line of sight.

In the operation of the apparatus as described above, the initial velocitymotor 22 and/or the wind component motor 50 have been employed for applying correctional displacements to the slides 32 and. 59 respectively under the control of the crank 89. It is possible, however, to perform this correcting operation by the cranks 25 and 5 3 and without using the corresponding motors.

Considering that the wind component crank 53 is to be employed, the parts will be retained in their normal condition as shown in Fig. 1 with the pinion 5! in mesh with the gear 48 and the circuit of motor 50 open at the contact elements and 51, the switch blade 6 also being inopen circuit position. Under these conditions the required wind component correction may be applied by operation of the crank 53 in the same way that the estimated wind component correction was initiallyapplied before commencing. the firing which showed that the actual trajectory point of impact 13 is as near the point of aim D as is requiredfor the desired accuracy of fire.

It will be, understood that in a similar manner.

corrections for errors in the estimated initial velocity may be applied by manipulation of the crank 25' in the same manner as described in connection with crank'53.

It will also be understood that while the instrument has been shown for computing corrections for certain ballistic factors 'itmay be used for other factors and that various changes may be made in its structural details without departing from the principal of the invention as defined in the appended claims. I

I claim:

1. In apparatus for determining the value of a ballistic factor affecting the trajectory of a projectile fired in accordance with a point 'of aim. representing a future position of a target, the.

combination of a calculating mechanism having settable elements, setting means for different elements, said mechanism and means being operable to calculate the firing data for the oint of aim and an estimated value of the ballistic factor, effective in the Plane of firing, and correctional means operable to actuate said mechanism and setting means to alter the ballistic factor until the calculated firing data is altered by the amount of the observed distance in the firing plane between the point of aim and the point of impact of a projectile fired'in accordance with the calculated firing data.

2. In apparatus for determining the value of a ballistic factor affecting the trajectory of a projectile fired in accordance with a range to a future position of a target, the combination of calculating mechanism comprising elements displaceable in accordance with the firing range, means adjustable by said elements and settable in accordance with the ballistic factor, said mechanism and means being operable to calculate the firing data for the range and an estimated value of the ballistic factor, and a control for said settable means operable to actuate the same and the mechanism to alter the ballistic factor until the firing data is altered by the amount of the observed difference between the point of aim for the range and the point of impact of a projectile fired in accordance with the calculated firing data.

3. In apparatus for determining the value of I I including a part settable in accordance with an differed from the desired one as explained in con i nection with Fig. 2.

The present correctional displacement of the I shaft 85 is transmitted by pinion 44, rack 43, arm 40 and pins 39 and 58 to slide 59 and then through 'pinionBli to the differential 34. The latter then works through the shaft 6|, bevel gears 62, shaft 63 and gears 64 and 65 to the differential 66 by which the cam 99 is actuated to control the motor 86, as previously described, to show by dial 82 the value of the correction being applied and by dial [8 the corrected value of the firing range. As in the operation of the instrument when the motor 50 is employed, the correct value of the wind component will be shown by dial l6 when the estimated value of the wind component, means for arbitrarily setting said part, and correctional means operable to replace the arbitrary control of said part to alter the wind component factor until the calculated firing data is altered by the amount of the observed difference between the point of aim and the point of impact of a projectile fired in accordance with the calculated firing data.

4. In apparatus for determining the value an initial velocity factor affecting the trajectory of a projectile fired in accordance with a point of aim representing a future position of a target,

' the combination of mechanism for calculating the firing data for the point of aim and an estimated value of the initial velocity factor, said mechathe point of impact of a projectile fired in accordance with the calculated firing data.

5. In a computing instrument, the combination a of a member adapted to be actuated in accordance with a factor of a point of aim representing a future position of a target, a second member adapted to be actuated in accordance with an estimated value of a ballistic factor related to the substantial plane of and affecting the trajectory of a projectile fired in accordance with the first factor, an element actuated by the combined actuations of the members for giving the data for firing the projectile, means for correcting the actuation of the second member in accordance with observed difference as related to said plane between the point of impact of a projectile fired in accordance with said data and the point of aim, and means for indicating the value of the second ballistic factor required for such corrections.

6. In a computing instrument the combination of a member adapted to be actuated in accordance with a factor of a point of aim, a second member adapted to be actuated in accordance with an estimated value of a ballistic factor affecting the trajectory of a projectile fired in accordance with the first factor, means for combining the actuation of the members, a part actuated in response to the operation of the combining means to give the correction required to the effect of the first factor, means actuated the part for giving the data required for firing the projectile, means for altering the last named means in accordance with the observed difference between the point of aim and the point of impact of a projectile fired in accordance with the firing data, and means for simultaneously actuating the second member to cause the combined actuation of the members to actuate the part an amount corresponding to the correction to the firing data.

7. In a computing instrument the combination of a member adapted to be actuated in accordance with the range of a point of aim, a second member, arbitrary setting means therefor adapted to be operated to actuate said second memher in accordance with an estimated value of a ballistic factor affecting the trajectory of a pro- .iectile fired at that range, said arbitrary setting means being adapted to be engaged with and disengaged from said second member, separate means for indicating the movement of the members. means for combining the actuations of the members to give the estimated correction, means for combining the movements of the first member and the combining means to give the firing range. and means substitutional for said arbitrary setting means and operable to correct the 8. In a computing instrument, the combination of a member adapted to be actuated in accordance with a factor of a point of aim, a second member adapted to be actuated in accordance with an estimated value of a ballistic factoraffecting the trajectory of a projectile fired in accordance with the first factor, separate means for indicating the movements of the members, means for combining the actuations of the members, means under the control of the combining means for indicating the combined actuations of the members and means for combining the combined actuations and the movement of the first member to give the data for firing the projectile and means for correcting the actuation of the second member in accordance with observed'dlfferences between'the point of aim and the point by the first member and o combined actuations of the actuation of the second member in accordance with the observed differences between the point of aim and the point of impact of a projectile fired in accordance with the firing range whereby the correct value of the ballistic factor will be shown by the indicating means for the second member.

of impact of a projectile fired in accordance with such data whereby the correct value of the ballistic factor will be shown by the indicating means for the second member.

9. In a computing instrument, the combination of a member adapted to be actuated in accordance with a factorof a oint of aim, a second member adapted to be actuated in accordance withan estimated value of a ballistic factor affecting the trajectory of a projectile fired in accordance with the first factor, separate means for indicating the movements of the members. means for combining the actuations of thememhere, means for indicating the combined actuations of the members, a power driven follow-up mechanism including controlling elements under the control of the combining means for actuating the last named indicating means and means for combining the movement of the means for indicating the combined actuations of the members with the movement of the first member to give the data for firing the projectile and means including the controlling elements of the follow-up mechanism for correcting the actuation of the second member in accordance with observed differences between the point of aim and the point of impact of a projectile fired in accordance with such data applied to the means for indicating the members, whereby the correct value of the ballistic factor will be shown by the indicating means for the second member. 10. In a computing instrument, the combination of a member adapted to be actuated in accordance with a factor of a point of aim, a second member adapted to be actuated in accordance with the actual value, of a ballistic factor affecting the trajectory of a projectile fired in accordance with the first factor, a third member adapted to be actuated in accordance with an estimated value of a second ballistic factor affecting the trajectory of a projectile fired in accordance with the first factor, means for combining the actuations of the first and second members, means for combining the actuations of the first and third members, an element actuated in response to the operation of the first member and both of the combining means for giving the data for firing the projectile and means for correcting the actuation of the third member in accordance with observed differences between the point of aim and the point of impact of a projectile fired in accordance with the firing data 2,89%?! part, an element representing a function of the factor, a second element representing a function of the factor, a device actuated jointly by the elements, means for manually actuating the second element, means for mechanically actuating the second element, means including the device to cause the second element to be actuated mechanically when the part is actuated manually and reversely to cause the part to be actuated mechanically when the second element is actuated manually such that the functions represented by the elements are the same.

12. An apparatus for determining values of ballistic factors deriving from a wind vector and an initial velocity, the combination of calculating mechanism comprising elements .displaceable in accordance with the firing range, means adjustable by said elements and settable in accordance with the respective ballistic factors, and said mechanism being operable to calculate firing data forrange and an estimated value of at least one ballistic factor, and control means operable to actuate the same and to alter the ballistic factors until the firing data are altered by the amount of the observed difference between the point of aim and the point of impact of a pro- J'ectile fired in accordance with the calculated firing data.

' HANNIBAL C. FORD. 

